Spin−Spin Interactions in Porphyrin-Based Monoverdazyl Radical Hybrid Spin Systems
Bibliographic record
Abstract
The spin-spin interactions in a complex consisting of a metalloporphyrin with a verdazyl radical attached at one of the beta positions of the porphyrin ring are investigated. The X-ray crystal structure of the copper porphyrin complex shows that the plane of the verdazyl moiety is oriented such that it is nearly perpendicular to the plane of the porphyrin ring so that weak magnetic interactions between the metal and radical are expected. Consistent with this expectation, magnetic susceptibility and continuous-wave electron paramagnetic resonance (EPR) measurements of the copper (d(9)) and vanadyl (d(1)) versions of the porphyrin show that the metal and radical are weakly antiferromagnetically coupled. Thus, the ground state is a singlet, but the triplet state is thermally accessible above approximately 5 K. Spin-polarized transient EPR measurements of the free-base analogue show that its lowest excited state is a quartet, indicating that the verdazyl radical couples ferromagnetically to the triplet excited state of the porphyrin. Low-temperature transient EPR measurements on the vanadyl porphyrin reveal that the lowest excited quintet state is populated. This implies that the antiferromagnetic coupling between the metal and radical observed in the ground state is switched to a ferromagnetic arrangement in the excited state by the presence of the unpaired electrons in the pi and pi* orbitals of the porphyrin.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".